Screw-thread gauging device



June 22, 1948. w, HUGHES 2,443,858

SCREW THREAD GAUGING DEVICE Filed Dec. 5, 1945 ATTORN EY F'atented June 22, 1948 OFFICE SGREWTHREAD GAUGING DEVICE GeorgeiW'." Hughes; Dayton, Ohio, assignor to'The Sheflield'Corporation, Dayton, Ohio; a corporation of Ohio Application- December 5, 1945;;Serial- No. 632,826

This invention relates t thread -gaugingfld'evices and more particularly to-devices-for gauging the thread lead :or pitch distance;

One object of the invention istheprovision of a thread gauging instrument havinghwork ens gaging membersformed to properly? interfijt threads-of diiferent sizesrsuch members: being. rotatably adjustable to bring .difierent portions of different shapesinto position ion engagement with the workpiece. y

Another objectfis the provisionflona -thread gauge having rotatably adjustable work engaging memberswhich have peripheral portions of trun cated- V-cross-sectiona1. form, the .amount oftruncation: increasing annularlyinv gradualltproa gression from a minimum amount'toa maximum amount so that, in a predeterminedrangeof size workpieces of different diameters on an= adjustable work holder can. be accurately gaugedgt" q Other objects andladvanta'ges ofl the-invention. will be apparent from the. following description, the. .appended claims and the accompanyin drawing, in which,

Fig.1 is atop plan View oi-athread-gauging instrument embodyingthe presentinvention; t

Fig. 2 is a side elevation of the gaugingmstrument; l Fig. 3 is an end view of'the'gauging instruhie'nt; Fig. 4' is a detaiLof one of the work" en aging members; I

Fig. 5 is an end view of the work-engaging'mem heir;-

Fig. 6 is a section of the'lin'e 6 -6 df'Fi'gidfand Fig. 7 is an enlarged detail showing intemengagement of? the work and the work engaging member ll- Referring more particularlyitothef drawin ifi'n which like parts "have been: given the same reference-numeralstin the several' views, I 0 designates a support or base which carries a pair of work engaging members. and 12 adapted to interfit with the threadsonwork piecesto be gauged. These members are relatively movable and. their relative positions are shown by'asuitable gauge l3 that operates electrical switches or control an indicator.-This instrumenam'ay be of the character shown in Patent 392,301, issued January. .8,:1946. The workpiecesto be gauged are' applied to a work holder or table 14 andlpre'sse'd against thetwo work engaging members ip the gauging operation.

The work engagin'g memberi l'l'comprises a rotatably adjustable disc the peripheral portion of I of the V are adapted-to engage-and interfitwith the side surfaces of the threads of workpieces of different sizes. This dis'cis secured; preferably in a permanent manner, to a shaft portionlB which is arranged in a ring IT. This ring includes positionof adjustment.

which is of truncated v shape i radial crosssectiom-seeFigs; 4, 5; and 6; inclinedfsides The sha'ft section [6 is provided'with' an index mark 2!! that cooperates with a series of radial markings 35 on the flat outer side of a disc 2| which isfixed to the base portion of the ring; The marking show the position of theshaft section in its annular setting. The base portion of the ring I! is carried bya spring supported bar 23 that extends in front of aicarrying'baridsw cured by suitable screws 2510 the top of the base I0; A pair of straight parallel spring blades 26 and 21 are fixed at their forward ends to-the-ends of the bar-23 andare secured at their other ends to the bar 24; These blades carry the bar 23 for parallel movement ina direction parallel to the axis of the shaft -l6,"or in other words parallel-to the axis of the workpiece; when thelatter is in positionto be gauged. A short post 28 i fixed on theybar 23' and bearsagainst the plunger 29 of the gauge l3; Aswill be apparent, the positioning of the work engaging member H, which is positionedbythe workpiece; will correspondingly positi'on the bar 2-3, the post- 28 and the plunger2'9.

The work engagingmember i2 also comprises a disci-denticalin construction to the discof the work engaging member l I-. It is securely fixed o'n a longer shaft portion 3llwh-ich' extends through a stationary ring- 31 the main portion otwhich is secured-to the upper part of the base: Ill A removable cap portion 32- normally held in clamp ingposition-against' the shaft 3 D by a-thumb screw 33 serves-to fix the work 'engagingmember 12 on the base l ili' The shaft portion iifl is long enough' so that the-disc-like work engaging portion canbe adjusted towards and from the work engaging member I l to accommodate workpieces of different lengths. The shaft portion 30 has an index mark 34* that cooperates with radially extending mar-list 5 on a graduated disc 3B fixed to the body portion of thering 3i The radially extending markings 35 onthe'disb 3W andon the'discll are similar. The rotational setting of the work engaging member can thus be readily determined;

and readily made to agree with the setting of the member ll.

The thread grooves of workpieces having many threads per inch are quite small, whereas workpieces having only four or five threads per inch, for example, are very much larger and will receive a very much wider fingeror. part. The peripheral portions of the work engaging members H and 12 are so formed that they will accommodate threads of any size in a predetermined size range. Thus, as shown in Fig. 4, the work engaging member II has a'periphery that provides a truncated V-shaped cross-section with they may be set by J ohansson blocks applied between those members after previously determining the exact allowance that must be made for the width of the disc portion of the work engaging members.

A high degree of care is unnecessary in setting the table I4 in its proper position to accommodate a thread workpiece of a particular size or diameter, for the relative spacing between the members I l and I2 will not be affected if the axis of the workpiece is a little above or a little below 1- .ithe horizontal plane of the centers of the work engaging members.

the amount of truncation increasing annularly in a gradual progression from a minimum amount to a maximum amount. Preferably the inclined peripheral sides of this memberare each geni eratecl by a straight line in the rotation of the member ll about the axis X, which corresponds to the axis of the shaft portion. to which this portion is secured. The flat periphery is ground eccentrically to the axis X, so the amount of truncation changes. Theangle of the inclined sides of the member H is about 2 degrees less than the angle included between the standard thread angle of the workpiece 44 so that only the outer portions of the work engaging member will contact the threads and the point of contact will be at the pitch diameter. At the point A the amount or" truncation is a minimum, the work engaging member at that point being adapted for engagement with a workpiece having many threads per-inch, its shape being sharp enough to reach into the small threads of the workpiece so as to be in firm engagement at the pitch diameter. At point B the'truncation is greater, while at C the amount of truncation is a maximum and there the work engaging member can interfit with the pitch diameter portions of threads of comparatively large size.

It willbe understood that the thumb screws I"?! and 33 can readily be loosened and the work engaging members rotated corresponding amounts by observing the indications on the shaft portions andon the graduated discs 2| and 3 6 so that the proper portions ofthe work engaging "members are presented towardsthe work position.

The table it provides a work supporting pro j jection 33 and a vertically adjustable side plate 39 having suitable graduations 40. A fastening screw ll extending through theslot t2 in the sideplate threads into the base It to secure the work holder in its desired position. Properly adjusted, the work holder carries the work, illustrated in dash lines in Fig. 3, so that the work axis lines up in the same plane with the axes of the work engaging members and with the central portions of the spring blades 26. The thrust of the work is therefore neither above nor below the spring blades. This obviates any tendency for a twisting. action on, the spring blades 26and 21.

In setting up the gauge a master thread may be applied to the work engaging members H and I2 after they have been adjusted so that they are far enough apart to give an adequate check, and after they have been rotatably adjusted to present the proper portions of their peripheries to the work. The reading on the gauge I3 is noted when this master is applied. When the workthe relative spacing of the members II and l2,

The annular setting of the work engaging members I l and I2 is not sensitive and need not be determined with great accuracy, for small errors in the rotational positioning of the members I l and 12 will not affect the relative spacing between those members. However, this rotational adjustment which brings differently formedV-shaped sections into position for engagement with the workpiece permits the gauge to very conveniently accommodate workpieces having any number of threads within the range of the instrument regardless of the pitch diameter of the threads. For example, exact checks can'be made on a workpiece of one inch diameter with 20 threads per inch, and on workpieces of /2 inch diameter with 8 threads per inch, and in each instance the proper engagement along the pitch diameters of the threads gauged.

While the'form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention defined in the appended claims.

What is claimed is:

1. In a thread gauging instrument, a work engaging member formed to interfit with threads of any size in a predetermined size range, said member comprising a rotatably adjustable circular disc having its periphery of truncated V-crosssectional form with the amount of truncation increasing, annularly in gradual progression from a minimum amount to a maximum amount.

2. In a thread gauging instrument, a work engaging member formed to interfit at the pitch diameter only with threads of any size in a predetermined size range, said member comprising a rotatably adjustable circular disc having its periphery of truncated V-cross-sectional form with the amount of truncation, increasing annularly in gradual progression from a minimum amount to a maximum amount, the angle included between the sides of the V being slightly less than the included angle of the standard thread form to be checked.

. GEORGE W. HUGHES;

1 REFERENCES CITED Y The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,456,938 Schoof Mar. 29, 1923 2,027,217 Zerkle mu..- Jan. 7, 1936 2,392,301 A1181 Jan..8, 1946 e FOREIGN PATENTS Number Country Date 378,483 .Italy 1940 555,893 Great. Britain 1943 

